The present invention relates generally to rollers used in various kinds of machinery and, in particular, to rollers used in continuous web conveying or converting machinery.
Because all kinds of conveying and converting systems utilize rollers, considerable attention has been given to improving their reliability, reducing bending of the tubing and reducing the inertial tension required to turn the roller. In web (i.e., continuous sheet) machinery, all kinds of materials, e.g., paper, plastic, tissue, foam, may be looped around a series of rollers. The rollers must have a necessary rigidity and strength to support a web load while withstanding the turning torque stress produced by the web. Rollers have been made of steel, aluminum or other metals to provide the necessary rigidity and strength. Yet, the materials themselves have inherent problems. For example, steel rollers require excessive horsepower to overcome the initial start-up inertia and to keeping the steel rollers turning.
Many patents disclose rollers and methods of making thereof. For example, U.S. Pat. No. 1,742,454 issued to Van Derhoef and U.S. Pat. No. 2,593,069 issued to Steinmetz teach methods of making roller rollers. U.S. Pat. No. 1,622,758 issued to Beulke et al.; U.S. Pat. No. 2,808,730 issued to Shank; and U.S. Pat. No. 3,958,837 issued to Chagawa disclose improved roller designs. U.S. Pat. No. 4,029,200 issued to Dillon teaches a roller design fabricated in plastic. U.S. Pat. No. 5,022,132 issued to Valster et al. and U.S. Pat. No. 5,568,976 issued to Gabriele disclose bearing mounts for rollers. U.S. Pat. No. 5,387,962 issued to Castelli et al. discloses a self-aligning roll for belt loop modules.
In continuous web making machinery, all kinds of materials, e.g., paper, plastic, tissue, film, fabric, foam, etc., may be transported through a nip formed between two rollers. The purpose of a nip between a pair of rollers is to exert pressure on the web material. As is generally known, it is desirable to produce a uniform pressure across the nip formed between the rollers.
One way to produce this desired result is to form a gradual crown on the outer surfaces of the rollers. The crown is in the form of a gradual increase in diameter of the roller toward the midpoint of the roller. When a crowned roller is combined with a straight roller or another crowned roller, and the ends of the opposed rollers are brought together, a uniform pressure can be produced along the entire length of the rollers as the rollers deflect under the applied load.
In many machines and systems, many different crowns are needed for various sized rollers. The process of crowning a roller requires extensive, precision machining, thereby resulting in substantial sums associated with labor and manufacturing costs. Moreover, in many machines and systems, many different rollers of different lengths and diameters are needed. This requires extensive fabrication, costing substantial sums for labor and parts, as well as requiring a large inventory of tubing and bearing assemblies. Notwithstanding these known rollers and bearing mounts, the art has not adequately responded to date with the introduction of an roller which reduces job specific construction by eliminating end plugs, balancing weights, and extensive machining.
Accordingly, the present invention provides a roller design which substantially reduces the need for crowning rollers used in nipped applications, and generally reduces job specific construction in other applications. In one aspect of the present invention, there is provided an inner tubing and an outer tubing concentrically disposed around the inner tubing. The inner tubing has an outer diameter and the outer tubing has an inner diameter which is larger than the outer diameter of the inner tubing. To fix the positions of the inner and outer tubing, e.g., weldments spaced a distance from each end of the tubings are suitably provided to secure the outer tubing to the inner tubing. During a nipped application, the outer tubing will pivot about the weldments to substantially provide a uniform pressure across the nip. This pivoting effect reduces the amount of crowning normally required for a particular nipped application.
In another aspect of the present invention, there is provided a method of assembling a roller as just described. The method includes providing an inner tubing and an outer tubing, placing the outer tubing around the inner tubing, positioning a fixture device at opposite ends of the roller to space the outer tubing away from the inner tubing, drilling a plurality of holes around the circumference of the outer tubing at a distance spaced inward from both ends of the roller, filling the holes with welding material to securely fasten the outer tubing to the inner tubing, and thereafter removing the fixture device from between the inner tubing and the outer tubing.
The foregoing design of an inner and outer tubing can be extended to other embodiments in which the inner and outer tubings are secured relative to each other by different means. Thus, in another aspect, the present invention provides a roller tubing, which includes an outer elongate tube; an inner elongate tube concentrically disposed within the outer tube; and a plurality of radially disposed spokes rigidly interconnecting the inner tube to the outer tube.
In yet another aspect, the invention provides a roller which includes a substantially cylindrical roller body having opposed ends. The roller body includes an outer elongate tube; an inner elongate tube concentrically disposed within the outer tube; a plurality of radially disposed spokes rigidly interconnecting the inner tube to the outer tube; and a pair of bearings, spaced apart and press fit into the inner surface of the inner tube, at a distance apart from the ends of the roller body.
In a further aspect, the invention provides a method of constructing an roller. The method includes the steps of (i) providing a length of a tubing having opposed ends, and including an outer elongate tube; an inner elongate tube having an inner surface, and concentrically disposed within the outer tube; and a plurality of spokes rigidly interconnecting the inner tube to the outer tube; (ii) inserting a bearing assembly into the inner surface of the inner tube at a distance apart from an end of the tubing material, the inner surface closely receiving the bearing assembly; and (iii) press-fitting a support shaft into the bearing assembly.
Other advantages and a fuller appreciation of the specific attributes of this invention will be gained upon an examination of the following drawings, detailed description of preferred embodiments, and appended claims. It is expressly understood that the drawings are for the purpose of illustration and description only, and are not intended as a definition of the limits of the invention.